Antioxidants – nature’s little helpers

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Antioxidants play a vital role in the body to protect against the degeneration of cells. Research suggests that antioxidants help to protect against cancer, stroke and heart disease. They may also help to delay the ageing process, reduce the formation of ‘bad’ LDL cholesterol and prevent the formation of cataracts.

Putting out fires

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So how do antioxidants work? Think of them as fire-fighters, putting out the fires created by unstable particles, called free radicals.

A free radical is an atom in the body that is damaged and missing one or more electrons, making it unstable. Free radicals roam around, searching for other atoms from which to steal electrons. When a stable atom has an electron stolen, it in turn becomes an unstable free radical. This starts a chain-reaction of electron-stealing throughout the body.

In come the fire-fighters, in the form of free radical scavengers. These atoms have extra electrons that they donate to free radicals, stopping the chain reaction. Antioxidants are a major source of free radical scavengers.

Free radicals can damage mitochondria (the energy powerhouse of a cell), rupture cell membranes and damage DNA, thereby altering or destroying cell function.

The body can normally cope with low levels of free radicals but high levels may initiate or contribute to premature ageing, atherosclerosis (a disease of the arteries) and heart disease, cancer, cataracts, arthritis, infertility in men and other degenerative diseases.

While oxygen is essential to life, it can also damage cells. The chemical process that occurs when oxygen damages cells is called oxidisation and it is this process that creates free radicals.

You can see oxidisation in action in your kitchen when fats become rancid or the flesh of an apple turns brown. This process is occurring in your body too.

Oxygen is not the only substance that causes oxidisation. These also contribute to the process:

  • Environmental pollution
  • Cigarette smoke
  • X-rays or radiation
  • Sunlight

Considering that all of these factors are frequently present in our contemporary way of life, it is virtually impossible to prevent the production of free radicals in our bodies. What we can do, however, is top up our levels of antioxidants to combat the activity of free radicals and therefore prevent disease. However, antioxidants cannot prevent disease alone: hereditary and other factors may be present that contribute to the development of disease.

Oxidisation and cholesterol

Antioxidants, such as Vitamin E, beta-carotene and lycopene (the red pigment in tomatoes) may help to stop damage occurring to the blood vessel walls by preventing the oxidisation of cholesterol within the body.

Oxidisation of ‘bad’ LDL cholesterol in the bloodstream is thought to play a key role in the development of fatty streaks and atherosclerosis in artery walls – and the accompanying increased risk of angina, heart attack and stroke.

Antioxidants are found in certain vitamins, minerals, enzymes and nutrients. They are also found in carotenoids, the pigments in fruits and vegetables that give them their red, yellow and orange colours. Another source of antioxidants are phytochemicals – non-vitamin compounds that are found in all fruits and vegetables.

Research has estimated that the risk of heart disease and cancer is considerably lower in people who consume five to seven serves of antioxidant-rich fruit and vegetables every day.

To make sure that you are getting enough carotenoids and phytochemicals, try to eat three different colours of fruit and vegetables every day to provide you with a range of colour pigments.

Vitamins

Vitamin Antioxidant action Food sources
Vitamin A Helps prevent the formation of free radicals by bonding to oxygen molecules. Promotes germ-killing enzymes, destroys carcinogens and is necessary for healthy mucous cells. The carotenoid beta-carotene is a form of Vitamin A and is one of the most powerful antioxidants to be found. Carrots, broccoli, squash, melon, spinach, other deep yellow and orange fruits and vegetables and other green, leafy vegetables. The stronger the colour of the fruit or vegetable, the higher the carotenoid content.
Vitamin C Guards against harmful reactions occurring within cells and traps free radicals before they enter cells. Recommended dosage is between 600 and 1,000 mg per day. Citrus fruits and juices, strawberries, kiwi fruit, tomatoes, broccoli, spinach, potatoes and capsicum.
Vitamin E Vitamin E improves the use of oxygen within the body and protects the coating around cells from free radical attack. Between 200 and 600 IU recommended daily. Vegetable oils, seeds, nuts, wheat germ, whole grain breads and cereals, green leafy vegetables.

Minerals

Mineral Antioxidant action Food sources
Selenium Stimulates increased antibody response to germ infection. Works very well in conjunction with Vitamin E. Between 100 and 200 mcg recommended per day. Brewer’s yeast, meat, oysters, salmon, tuna, cashews and whole grains.
Zinc Required for protein synthesis and collagen formation. Promotes a healthy immune system. Between 25 to 30 mg recommended per day. Fish and other seafood, legumes, soy products and whole grains.

Enzymes, nutrients and fatty acids

Enzyme Antioxidant action Food sources
Alpha lipoic acid The body produces its own alpha lipoic acid, a vitamin-like fatty acid that plays a large role in energy production within cells. Red meat, potatoes, carrot, spinach.
Gamma-Linoleic Acid (GLA) An omega-6 fatty acid. Hydrogenated vegetable oils, margarine or a high-fat diet can block the body’s ability to convert food to GLA. The body creates its own GLA from linoleic acid, found in vegetable oils. Evening primrose oil, black currant seed oil and borage oil.
L-Cysteine Used by the liver and lymphocytes to detoxify the body. Works best when taken with vitamin E and selenium. Garlic
L-Glutathione An amino acid that works as a detoxifier to rid the body of free radicals produced from metals, drugs, cigarette smoke and alcohol. Studies have shown that L-Glutathione is not increased in the body by taking supplements. Present in most plant and animal food sources.
Superoxide dismutase (SOD) An enzyme that revitalizes the cells and reduces the rate of cell destruction. Removes the most common free radical, superoxide, and helps the body use zinc, copper and manganese. Studies have shown that SOD is not increased in the body by taking supplements. Barley and wheat grasses, broccoli, brussel sprouts, cabbage and most green plants.
Coenzyme Q-10 Helps the body produce energy at a cellular level. Protects and strengthens the heart and slows the shrinking of the thymus (one of the body’s main immune organs) which occurs with age. People over 35 could consider using a Coenzyme Q-10 supplement. Fish, red meat, eggs, spinach some grains and beans.

Carotenoids

These are the red, yellow and orange pigments found in fruits and vegetables. As well as having antioxidant properties, they are thought to be potent cancer fighters. Beta-carotene (Vitamin A) is one of the most powerful antioxidants (see above).

Carotenoid Antioxidant action Food sources
Lycopene Gives tomatoes their red colour. Lycopene is linked to a lower risk of prostate cancer in men. In one study, men who ate at least ten servings of tomato-based foods every week had a 45 per cent reduced risk of developing prostate cancer. May also reduce cholesterol oxidisation. Tomatoes, tomato sauce, tomato puree.
Lutein and zeaxanthin Linked to eye health in the elderly. Spinach and broccoli.

Phytochemicals

Phytochemicals are found in all fruits and vegetables. Early research is speculative but shows them to be potential cancer protectors. They seem to interact with every step of the cancer process, by slowing, stopping or reversing cancers.

Phytochemical Antioxidant action Food sources
Flavonoids Include catechins. Green and black tea, red wine.
Isoflavones Include phytoestrogens, plant hormones that are very weak versions of the human hormone oestrogen.  However, due to the way in which phystoestrogens in soy may react with certain treatment medications, people who have had breast cancer should always consult with a doctor before eating soy products or other phytoestrogen foods. Soy foods.
Lignans Lignans are a type of phytoestrogen (see above). High lignan intake is associated with reduced rates of breast, prostate and colon cancer in population studies. Plant foods, soy beans, sesame seeds and flax seed.

Other phytochemicals include indoles and isothiocyanates (mainly responsible for broccoli’s ant-cancer reputation), organosulphur compounds in garlic and onions, monoterpenes in citrus fruits and caraway seeds, saponins in soybeans, nuts and chickpeas, and cruciferous chemicals with anti-cancer properties in broccoli, cabbage, cauliflower and brussel sprouts.

Supplements vs. the real thing

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Foods provide a range of antioxidants and may be better for you than taking single vitamin supplements in tablet form, such as vitamin E or vitamin C tablets. Antioxidants work together and help each other in the body, so the combination of antioxidants obtained naturally from foods works more effectively than single supplements. You may like to choose an antioxidant supplement formula that contains a range of antioxidants, but remember that vitamin supplements should never replace a healthy diet.

It’s also important not to go overboard. Studies have shown that extremely high doses of antioxidants may damage cells in much the same way  free radicals do.

Calorie King
CalorieKing's mission is to provide the best information, tools and education to Australians to help them conquer their weight.

CalorieKing is the brainchild of Allan Borushek, registered dietitian, co-found here at food.com.au and author of "Allan Borushek's Pocket Calorie & Fat Counter", Australia's best-selling calorie counter for over 30 years.

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